The present invention relates to an acoustic system that is furnished with a howling prevention capability.
With acoustic systems in which an audio signal inputted from a microphone is amplified and outputted from a speaker, when the microphone is brought close to the speaker or when the output level from the speaker is raised, there are times when howling occurs. This is caused by the occurrence of an oscillation state in which the sound outputted from the speaker feeds back into the microphone.
For some time, many proposals have been made in order to prevent this howling. For example, Japanese Patent Publication Number 2773656 discloses an acoustic system which emits a white noise into space from a speaker as a test signal, the sound in the space is input to a microphone. The disclosed acoustic system then measures the frequency characteristics of the space, and uses the measurement results to determine the frequency characteristics of a filter. Thus, the production of the howling is prevented by the reduction of the level of a specific frequency.
However, with the acoustic system described above, there is the problem that because a white noise is generated as a test signal, it grates extremely on the human ear. In addition, in those cases where a wave such as a sine wave is used as the test signal, together with grating on the ear in the same manner, there is also a weakness that a large number of test signals covering the entire range of the audible frequency band must be generated. Thus, it takes a long time to generate the signals while successively changing the frequencies, making the processing complicated.
The present invention addresses problems as discussed above and has as an object the provision of an acoustic system that has a simple configuration and that generates a test signal that is satisfactory with regard to avoiding grating on the human ear.